JPH06249078A - Method for judging failure of exhaust gas recirculating device - Google Patents

Abstract

PURPOSE:To avoid erroneous judgement due to variation of the rotational speed of an engine by correcting at least one of the differential pressure or a prescribed range of intake pressure before and after the opening and closing of an EGR valve according to a difference between the rotational speeds of an engine. CONSTITUTION:An EGR valve 9 is adapted to close a path 8 when a negative pressure chamber 9a communicates with the atmosphere and opened when the negative chamber 9a is connected to an intake path 2 and supplied with manifold pressure (negative pressure) to circulate a portion of exhaust gas in an exhaust path 7 through the path 8 to the intake path 2. The rotational speed of an engine 1 is detected respectively before and after the opening and closing of the EGR valve 9 to correct at least one of the differential pressure or a prescribed range of intake pressure before and after the opening and closing of the EGR valve 9 according to a difference between the rotational speeds. Thus, the erroneous judgement of a failure in the exhaust gas recirculating device(EGR) can be avoided to judge correctively the failure in the EGR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device failure determination method.

[0002]

Exhaust gas components of a gasoline engine are mainly carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx), which are contained in the air-fuel mixture due to the high temperature during combustion. Most of the nitrogen oxides contained in the exhaust gas of an automobile are NO, which are produced by the reaction between nitrogen and oxygen. Even if the air-fuel ratio is the same, if the amount of the inactive component in the air-fuel mixture is increased, the combustion temperature is lowered and the generation of NO is reduced. An exhaust gas recirculation device (hereinafter referred to as “EGR”) is a device that purifies the exhaust gas by returning a part of the exhaust gas to the intake system as the inactive component and adding it to the mixture.

As a method of diagnosing this EGR failure,
There is a "diagnosis method for exhaust gas recirculation control device" disclosed in JP-A-2-9937. This diagnostic method is executed when the engine is in the deceleration region where fuel cut is being performed.When the engine is in a stable state after completion of warming up, the microcomputer system opens and closes the negative pressure switching valve. The intake air pressure is introduced into the negative pressure passage, and the exhaust gas recirculation is performed so that the intake pressure can act on the negative pressure chamber of the EGR valve via the EGR modulator. When the pressure difference between the atmospheric pressure and the intake pressure after recirculation is less than the set value, it is determined that the EGR is out of order.

That is, as shown in FIG. 1A, when the throttle valve is fully closed (deceleration region), the EGR check mode is turned on to start the EGR check (FIG. 1B).
EGR is forcibly turned on and off until a check is completed after a predetermined time has elapsed ((d) in the figure), and the intake pressure, that is,
If the amount of change ΔP in intake manifold pressure (hereinafter referred to as “manifold pressure”) ((c) in the figure) is above a predetermined range, it is normal (shown by a solid line), and if it is less than the predetermined range, it is a failure (shown by a two-dot chain line). It is determined that there is.

[0005]

However, when the engine speed changes during the EGR check, the failure diagnosis method cannot accurately determine the failure of the EGR because the manifold pressure changes accordingly. For example, as shown in FIG. 2, when the engine speed Ne decreases between the EGR check start time A and the check completion time B when the throttle is fully closed, the manifold pressure increases as shown by the solid line in FIG. 1 (e). As a result, the engine is judged to be normal despite the EGR failure ((c) in the figure), or conversely, the engine speed increases between the EGR check start time B and the check completion time A. Then the manifold pressure is shown in Fig. 1 (e).
When it decreases as indicated by the dotted line, there is a problem that it is determined as a failure although the EGR is normal ((c) in the same figure).

The present invention has been made in view of the above points, and corrects the intake pressure according to the amount of change in the engine rotation speed from the start time to the completion time of the EGR check to make a mistake due to the change in the engine rotation speed. An object of the present invention is to provide a method of determining a failure of an exhaust gas recirculation device that avoids the determination.

[0007]

To achieve the above object, according to the present invention, an EGR valve provided in a passage that connects an exhaust passage and an intake passage of an engine is temporarily provided in a deceleration region of the engine. In the exhaust gas recirculation device failure determination method, the exhaust gas recirculation device failure determination method is performed, in which the exhaust gas recirculation device is opened and closed, and the intake pressure difference before and after the opening and closing is determined to be within a predetermined range. The rotational speeds of the engine before and after opening and closing are respectively detected, and at least one of the differential pressure of the intake pressure before and after opening and closing the EGR valve or at least one of the predetermined ranges is corrected according to the rotational speed difference.

[0008]

In the deceleration region of the engine, the EGR valve is temporarily turned on and off to detect the differential pressure of the intake pressure to detect the EGR.
When performing the check of EGR check, the rotational speed of the engine at the start and completion of the EGR check is detected, and the detected differential pressure of the intake pressure or the like is corrected according to the rotational speed difference to determine the engine rotational speed. Avoid misjudgment due to fluctuations.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 3 shows an outline of an exhaust gas recirculation system to which the method of the present invention is applied. A bypass passage 4 that bypasses the throttle valve 3 is provided in the intake passage 2 of the engine 1, and the bypass passage 4 is idle. A speed control valve (hereinafter referred to as “ISC valve”) 5 is provided. The EGR valve 9 is interposed in a passage 8 that connects a downstream side of the surge tank 6 of the intake passage 2 and an upstream side of the exhaust passage 7 to the catalyst device, and recirculates a part of the exhaust gas (recirculation) to the intake passage 2. ). The negative pressure chamber 9a of the EGR valve 9 is connected to the intake passage 2 on the downstream side of the throttle valve 3 and can communicate with the atmosphere via an EGR solenoid valve (electromagnetic valve) 10.

The EGR valve 9 is closed when the negative pressure chamber 9a communicates with the atmosphere to close the passage 8, and the negative pressure chamber 9a is connected to the intake passage 2 to supply the manifold pressure (negative pressure). Then, the valve is opened and a part of the exhaust gas in the exhaust passage 7 is returned to the intake passage 2 through the passage 8. EGR solenoid valve 10
Is opened when deenergized (OFF) to communicate the negative pressure chamber 9a of the EGR valve 9 with the atmosphere, and closed when energized (ON) to communicate the negative pressure chamber 9a of the EGR valve 9 with the intake passage 2. Let

An engine rotation sensor 11 for detecting the rotation of a crankshaft is provided in the engine 1, a pressure sensor 12 is provided in the surge tank 6 of the intake passage 2, and an O ₂ is provided in the exhaust passage 7.
A sensor 13 is provided. Electronic control unit (ECU)
15 is an engine rotation sensor 11, a pressure sensor 12, O
₂ sensor 13, air flow sensor, idle switch (turns on when throttle valve 3 is fully closed), cooling water temperature sensor, air conditioner switch, power steering switch, etc. (not shown) From the engine rotation sensor and the air flow sensor to calculate the intake air amount (A / N) per cylinder, engine speed, A / N, operating state of each auxiliary machine and exhaust gas. The fuel injection amount from the injector 14, the valve opening degree of the ISC valve 5, the valve opening degree of the EGR valve 9, etc. are set according to the oxygen concentration tow in the inside. The ISC valve 5 is driven by a stepper motor, and the EGR solenoid valve 10 is duty-controlled.

When the EGR valve 9 opens and closes (ON-OFF), the internal pressure of the surge tank 6 changes with the change of the EGR flow rate, and the EGR flow rate when the EGR valve 9 is open (ON) is smaller than that in the normal state. Since the pressure change is less than or equal to the predetermined value, it is possible to detect the EGR failure. Further, in order to suppress the torque fluctuation of the engine due to the opening and closing of the EGR valve 9 as much as possible, the EGR failure determination is monitored in the deceleration region (zone).

A method of determining a failure of the exhaust gas recirculation device will be described below with reference to the flow charts of FIGS. The electronic control unit 15 first initializes all flags and timers necessary for failure determination (step S in FIG. 4).
1) It is determined whether or not it is in the EGR check zone (step S2). In this EGR check zone, the engine rotation speed Ne is a predetermined rotation speed equal to or higher than the idle rotation speed, for example, 1300 rpm or higher (Ne ≧ 1300 rp).
m) and the deceleration region where the idle switch is on (FIG. 6). Then, when the engine is not in this EGR check zone, the process returns to step S1, and when it is in the EGR check zone, it is determined whether or not the engine has stayed in the EGR check zone for a predetermined time T ₁ or more (step S3). If the determination result in step S3 is negative (NO), the process returns to step S2, and if affirmative (YES), the EGR solenoid valve 10 is turned off to close the EGR valve 9 and EGR is turned off (step S4). After turning off, it is determined whether a predetermined time T ₂ has elapsed (step S5).

The time T ₁ in step S3 is a confirmation timer time for confirming that the operating region of the engine is the EGR check zone, and the time T ₂ in step S5 is a confirmation timer for the EGR off state. It's time. Then, the electronic control unit 15 determines that the monitor condition for the EGR failure determination is satisfied when these times T ₁ and T ₂ have elapsed (FIG. 11A).

The electronic control unit 15 returns to step S2 when the determination result of step S5 is negative (NO), and determines whether the flag F is 1 when the determination result is affirmative (YES), that is, when the monitor condition is satisfied. Judge (step S
6). At this time, the flag F is still 0, so the determination result is negative (NO) and the EGR check is started. Then, after the manifold pressure (P ₁ ) and the engine speed (Ne ₁ ) at the start of the EGR check are stored in the memory (step S7), the flag F is set to 1 (step S8). Next, the electronic control unit 15 determines whether or not it is in the EGR check zone (step S9),
When in the EGR check zone, the EGR solenoid valve 10 is turned on (FIG. 11 (b)), and EGR is turned on (step S10). When not in the EGR check zone, the process returns to step S1.

The electronic control unit 15 judges whether or not a predetermined time T ₃ (for example, 1 second) has elapsed after turning on the EGR (step S11), and when the predetermined time T ₃ has not elapsed, a step S9. Return to and repeat the judgment. This time T ₃ is sufficient to confirm that EGR is on (EGR valve 9 is open). The electronic control unit 15 completes the EGR check when the determination result of step S11 is affirmative (YES), that is, when a predetermined time T _{3 has} elapsed after turning on the EGR, and the manifold pressure (P ₂ ) at the time of completion of the EGR check is set. Engine speed (Ne ₂ )
Are stored in the memory (step S12), and the engine speed Ne ₂ and EG at the time of completion of the EGR check are stored.
Calculated rotational speed difference between the engine rotational speed Ne ₁ of R check start time point (Ne ₂ ~Ne _1), calculates the rotational speed correction value P _CNE Mani pressure according to the rotational speed difference (step S13).

The correction value P _CNE is calculated as follows. That is, the amount of change in engine speed (rpm)
And the manifold pressure are in a substantially proportional relationship as shown in FIG. 7, and therefore,
The correction value P _CNE of the manifold pressure corresponding to the rotational speed difference (Ne _{2 to} Ne ₁ ) can be obtained (FIG. 8). Therefore, the relationship between the rotational speed difference (Ne _{2 to} Ne ₁ ) and the correction value P _CNE is stored in the map, and the calculated rotational speed difference (Ne _{2 to} N ₁ ) is stored.
e ₁ ) Read out the correction value P _CNE according to.

The electronic control unit 15 controls the manifold pressure P ₂ when the EGR check is completed and the manifold pressure P when the EGR check is started.
₁ and the differential pressure (ΔP = P ₂ -P ₁₎ the rotational speed correction value P Mani pressure according to the rotational speed difference obtained in step S13
_CNE is added to correct the manifold pressure according to the engine speed fluctuation. That is, as shown in FIG. 9, the engine speed at the EGR check start time A is 2500 rpm.
When the engine rotation speed at the EGR check completion time point B decreases to 1500 rpm, the manifold pressure accordingly rises to point B on the solid line. Therefore,
When the manifold pressure is corrected by subtracting the correction value P _CNE according to the rotation speed difference of 1000 rpm, for example, the two-dot chain line is obtained, and the manifold pressure at the time of completion of EGR check becomes the point B ′.

When the engine speed at the EGR check start time point B is 1500 rpm and the engine speed at the EGR check completion time point A rises to 2500 rpm as shown in FIG. The pressure drops to point A on the solid line. Therefore, when the manifold pressure is corrected by adding the correction value P _CNE corresponding to the rotation speed difference of 1000 rpm, for example, a two-dot chain line is obtained.
The manifold pressure at the time of GR check completion is point A '.

In the electronic control unit 15, the manifold pressure (P ₂ -P ₁ + P _CNE ) corrected according to the engine speed difference that has changed from the start to the end of the EGR check is the failure determination value ΔP _EGR ( FIG. 11 (c), the determination whether the (d)) or in which _{(P 2 -P 1 + P CNE} ≧ ΔP EG R) ( step S14), and the determination result is affirmative (YES), the EGR is normal It is determined that there is (step 15), and if the determination is negative (NO), it is determined that the EGR is out of order (step 16). The electronic control unit 15 executes step S1.
When it is determined that the EGR is out of order in 6, the EGR check lamp (not shown) is turned on (FIG. 11 (e),
(F)) Inform the driver that the EGR is out of order.

In the above embodiment, the difference in engine speed (Ne ₂ -N ₂₎ before and after the opening and closing of the EGR valve is used.
e ₁ ), a correction value P _CNE is obtained, and this correction value P _CNE
Although the differential pressure (P ₂ −P ₁ ) of the manifold pressure is corrected with, the failure determination value ΔP _EGR may be corrected with the correction value P _CNE instead of the differential pressure (P ₂ −P ₁ ). .

[0022]

As described above, according to the present invention, E
There is an effect that it is possible to avoid erroneous determination of failure of the exhaust gas recirculation device due to fluctuation of the engine speed during the GR check, and to correctly determine failure of the device.

[Brief description of drawings]

FIG. 1 is a time chart of a method for determining a failure of an exhaust gas recirculation device.

FIG. 2 is a graph showing the relationship between manifold pressure and engine speed.

FIG. 3 is a diagram showing an outline of an exhaust gas recirculation system for an engine for carrying out a failure determination method for an exhaust gas recirculation system according to the present invention.

FIG. 4 is a part of a flow chart showing a procedure of a failure determination method for an exhaust gas recirculation device according to the present invention.

FIG. 5 is the rest of the flowchart showing the procedure of the method for determining the failure of the exhaust gas recirculation device according to the present invention.

FIG. 6 is a diagram showing an example of a monitor zone (deceleration region) for determining a failure of the exhaust gas recirculation device according to the present invention.

FIG. 7 is a graph showing the relationship between the amount of change in engine speed and the manifold pressure.

FIG. 8 is a diagram showing an example of a map in which a correction value of the manifold pressure according to the rotation speed of the engine is stored.

FIG. 9 is a diagram showing correction of manifold pressure due to a decrease in engine rotation speed when a failure of the exhaust gas recirculation device is determined.

FIG. 10 is a diagram showing correction of manifold pressure accompanying an increase in engine rotation speed at the time of failure determination of an exhaust gas recirculation device.

FIG. 11 is a time chart showing an outline of the operation of the exhaust gas circulation device shown in FIG.

[Explanation of symbols]

1 Engine 2 Intake Passage 3 Throttle Valve 4 Bypass Passage 5 ISC Valve 6 Surge Tank 7 Exhaust Passage 9 EGR Valve 10 EGR Solenoid Valve 11 Engine Rotation Sensor 12 Pressure Sensor 13 O ₂ Sensor 15 Electronic Control Unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazutoshi Noma 5-3-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Yasuhisa Yoshida 5-33-8 Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. An EGR valve provided in a passage that connects an exhaust passage and an intake passage of an engine is temporarily opened and closed in a deceleration region of the engine, and a differential pressure of intake pressure before and after the opening and closing is within a predetermined range. In the exhaust gas recirculation device failure determination method for determining whether or not there is an exhaust gas recirculation device failure, in the exhaust gas recirculation device failure determination method, the engine rotation speeds before and after the EGR valve opening and closing are detected respectively, and the rotation speed difference is detected. A method for determining a failure of an exhaust gas recirculation device, characterized in that at least one of the differential pressure of the intake pressure before and after the opening and closing of the EGR valve or the predetermined range is corrected in accordance with the above.